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https://github.com/pfloos/quack
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118 lines
2.8 KiB
Fortran
118 lines
2.8 KiB
Fortran
subroutine UCC_lda_exchange_derivative_discontinuity(nEns,wEns,aCC_w1,aCC_w2,nGrid,weight,rhow,Cx_choice,doNcentered,kappa,ExDD)
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! Compute the unrestricted version of the curvature-corrected exchange ensemble derivative
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implicit none
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include 'parameters.h'
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! Input variables
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integer,intent(in) :: nEns
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double precision,intent(in) :: wEns(nEns)
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double precision,intent(in) :: aCC_w1(3)
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double precision,intent(in) :: aCC_w2(3)
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integer,intent(in) :: nGrid
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double precision,intent(in) :: weight(nGrid)
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double precision,intent(in) :: rhow(nGrid)
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integer,intent(in) :: Cx_choice
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logical,intent(in) :: doNcentered
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double precision,intent(in) :: kappa(nEns)
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! Local variables
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integer :: iEns,jEns
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integer :: iG
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double precision :: r
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double precision,allocatable :: dExdw(:)
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double precision,external :: Kronecker_delta
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double precision :: a1,b1,c1,w1
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double precision :: a2,b2,c2,w2
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double precision :: dCxdw1,dCxdw2
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! Output variables
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double precision,intent(out) :: ExDD(nEns)
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! External variable
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double precision,external :: electron_number
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! Memory allocation
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allocate(dExdw(nEns))
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! Parameters for N -> N-1
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a1 = aCC_w1(1)
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b1 = aCC_w1(2)
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c1 = aCC_w1(3)
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! Parameters for N -> N+1
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a2 = aCC_w2(1)
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b2 = aCC_w2(2)
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c2 = aCC_w2(3)
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w1 = wEns(2)
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w2 = wEns(3)
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select case (Cx_choice)
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case(1)
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dCxdw1 = (0.5d0*b1 + (2d0*a1 + 0.5d0*c1)*(w1 - 0.5d0) - (1d0 - w1)*w1*(3d0*b1 + 4d0*c1*(w1 - 0.5d0)))
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dCxdw2 = 0.d0
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case(2)
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dCxdw1 = 0.d0
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dCxdw2 =(0.5d0*b2 + (2d0*a2 + 0.5d0*c2)*(w2 - 0.5d0) - (1d0 - w2)*w2*(3d0*b2 + 4d0*c2*(w2 - 0.5d0)))
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case(3)
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dCxdw1 = (0.5d0*b1 + (2d0*a1 + 0.5d0*c1)*(w1 - 0.5d0) - (1d0 - w1)*w1*(3d0*b1 + 4d0*c1*(w1 - 0.5d0))) &
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* (1d0 - w2*(1d0 - w2)*(a2 + b2*(w2 - 0.5d0) + c2*(w2 - 0.5d0)**2))
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dCxdw2 = (1d0 - w1*(1d0 - w1)*(a1 + b1*(w1 - 0.5d0) + c1*(w1 - 0.5d0)**2)) &
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* (0.5d0*b2 + (2d0*a2 + 0.5d0*c2)*(w2 - 0.5d0) - (1d0 - w2)*w2*(3d0*b2 + 4d0*c2*(w2 - 0.5d0)))
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case default
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dCxdw1 = 0d0
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dCxdw2 = 0d0
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end select
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dCxdw1 = CxLSDA*dCxdw1
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dCxdw2 = CxLSDA*dCxdw2
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dExdw(:) = 0d0
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do iG=1,nGrid
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r = max(0d0,rhow(iG))
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if(r > threshold) then
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dExdw(1) = 0d0
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dExdw(2) = dExdw(2) + weight(iG)*dCxdw1*r**(4d0/3d0)
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dExdw(3) = dExdw(3) + weight(iG)*dCxdw2*r**(4d0/3d0)
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end if
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end do
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ExDD(:) = 0d0
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do iEns=1,nEns
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do jEns=2,nEns
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ExDD(iEns) = ExDD(iEns) + (Kronecker_delta(iEns,jEns) - wEns(jEns))*dExdw(jEns)
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end do
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end do
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if(doNcentered) ExDD(:) = kappa(:)*ExDD(:)
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end subroutine UCC_lda_exchange_derivative_discontinuity
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